(1) Field of the Invention
The present invention relates to relieving excess pressure from high pressure vessels. More particularly, the present invention is directed to a pressure release device which is comprised of a strain sensitive area formed in the top or bottom of a pressure vessel. This safety device is activated by the physical distortion of the vessel end walls which results from over-pressurization. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
Various devices for venting excess pressure from an over-pressurized vessel are known in the prior art. These prior art devices are all directly responsive to an increase of the pressure within the vessel above a safe limit.
The most commonly used pressure release device is a spring loaded pressure release valve which is installed within an opening prepared in the vessel wall. A major disadvantage incident to the use of such values is the comparatively high cost of the spring loaded device itself and the additional cost of installing the device within the wall of the vessel. Furthermore, it may be disadvantageous to use such spring loaded valves within vessels that store corrosive material which would deteriorate the spring mechanism of the device and hinder its performance.
Another prior art approach to pressure relief involves welding a safety device within an aperture formed in the wall of a vessel. The thus installed devices are activated by increased pressure and are exemplified by the disclosure of U.S. Pat. Nos. 2,380,964 and 2,951,614. The disadvantage to these devices are the additional expense in mounting the device within the wall of the vessel, particularly the energy costs since resistance welding is the commonly employed attachment technique, and the difficulty in accurately fabricating the device so that they will uniformly be activated at a given pressure.
Still other devices have been developed which release pressure from aerosol cans. Examples of such other devices may be found in U.S. Pat. Nos. 3,292,826 and 3,815,534. A major limitation with the devices of the type depicted in these patents is that they are sensitive to relatively small pressure changes and would be ineffective for use with high pressure vessels.
A major disadvantage to all of the above-mentioned prior art devices is the additional expense incident to incorporating a separately fabricated pressure sensitive device within the wall of the vessel or container. Another major disadvantage that the prior art devices are universally responsive to the increasing pressure within the vessel and thus require exact machining to insure release at a given pressure.